1. Field of the Invention
The present invention relates to an elevator, and more particularly, to an elevator with a governor.
2. Description of the Related Art
These days, traction-type elevators, such as the ones disclosed in Published Examined Japanese Patent Applications Nos. 49-36192 and 51-17613, prevail in the art. In the elevators of this type, a cab and a counterweight are connected by means of a main rope, such as a wire rope, which is wound around a hoist in a mechanical room at the top portion of an elevator path. The cab is moved up and down along the path as the main rope is run by means of the hoist.
Recently, moreover, automatic traveling elevators, such as the one disclosed in Published Unexamined Japanese Utility Model Application No. 62-136476, have started to be developed. In the elevators of this type, a linear motor is used having a normally conductive or superconductive magnet or the like as its drive source, and a cab is moved up and down without using the main rope.
In general, an elevator comprises a cab, having a cab frame and a cab body, and a pair of guide rails, right and left, arranged along an elevator path. The cab is guided and supported for up-and-down motion along the guide rails, by means of roller guides which are arranged individually on the right- and left-hand sides of its top and bottom. Right- and left-hand emergency stop devices for engaging the guide rails are arranged at the lower portion of the cab.
The elevator further comprises a governor which detects an excessive speed of the cab and actuates the emergency stop devices in case the traveling speed of the cab exceeds a predetermined speed from any reason. Conventionally, the governor includes a governor pulley provided at the upper end of the path, a tension sheave at the lower end of the path, and an endless governor rope passed around and between the pulley and the sheave and extending substantially throughout the length of the path. A part of the governor rope is connected to a safety link which is mounted on the cab frame. As the cab moves up or down, the governor rope travels, so that the governor pulley is rotated.
The governor pulley is rotatably supported on a stand arranged at the upper portion of the elevator path, and a rope clamping mechanism for holding the governor rope is located near the governor pulley. Further, the governor pulley is fitted with a pair of flyweights which rotate together therewith. In a traction-type elevator, for example, the governor pulley and the clamping mechanism, along with the hoist, control board, etc., are arranged in the mechanical room at the upper end of the path.
According to the elevator with the governor constructed in this manner, if the cab travels at a speed higher than the predetermined speed for any reason, the governor pulley correspondingly rotates at a speed higher than its predetermined speed. As the governor pulley rotates at this high speed, the paired flyweights spread out by means of centrifugal force, thereby actuating the rope clamping mechanism. Thereupon, the clamping mechanism clamps the governor rope, so that the rope is stopped from traveling despite the movement of the cab. As a result, the safety link, connected to the governor rope, rocks so as to actuate the emergency stop devices, whereupon the stop devices seize and stop the cab immediately.
According to the governor of the conventional elevator described above, however, the endless governor rope is expected to extend in the elevator path substantially throughout its length. If the path is very long, as in an elevator of a high building, the governor rope should be made very long and thick enough for safe operation. In this case, the force of inertia produced during the travel, as well as the gross weight of the rope, increases. Accordingly, the governor pulley, tension sheave, etc. for supporting the governor rope must be very strong, and the rope clamping mechanism for stopping the travel of the rope should be an extremely high-powered one. Inevitably, therefore, the whole governor is large-scaled, requiring an increased installation space in the travel path. Thus, besides requiring space for the actual movement of the elevator, a wide space is needed for the governor. This is adverse to effective utilization of the building space, and entails an increase in manufacturing cost. As the governor rope is lengthened, moreover, its vibration, deflection etc., increase, so that the operations of the governor and the cab must be controlled in consideration of such vibration and deflection of the rope, as well as the aforesaid weight and force of inertia. Consequently, operational control for the whole elevator is highly complicated.
In the case of the automatic traveling type, in particular, the cab can be moved up and down without using the main rope, so that the elevator may possibly enjoy a very long path of 1,000 m or more. If the governor with the aforesaid construction is used, however, the extended elevator path requires use of a long governor rope, so that the above-described problems become more serious. Thus, the advantages of the automatic traveling elevator cannot be fully utilized.
Since the main rope need not be used, in the case of the automatic traveling elevator, furthermore, it is possible that the cab could run along a ring-shaped travel path which combines vertically extending paths and horizontally extending paths. If this elevator is used in combination with the aforementioned governor, however, the arrangement of the governor rope at the junctions between the vertical and horizontal paths is very difficult. If a plurality of cabs are arranged in one travel path, as many governor ropes as there are cabs are necessary, so that the rope arrangement is further complicated.